Subject: RTP port range question

From: Parekh Rishabh-crp049 <[email-masked]>
Date: Wed, 27 Oct 1999 09:16:20 -0500

I have a question regarding the UDP ports used for RTP. Here is an excerpt
from RFC 1889.

"RTP relies on the underlying protocol(s) to provide demultiplexing of RTP
data and RTCP control streams. For UDP and similar protocols, RTP uses an
even port number and the corresponding RTCP stream uses the next higher
(odd) port number. If an application is supplied with an
odd number for use as the RTP port, it should replace this number with the
next lower (even) number."

Does RTP use an even UDP source port or an even UDP destination port? 

Thanks to all who reply,
Rishabh Parekh
Motorola

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From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 27 Oct 1999 11:21:40 -0400

> Does RTP use an even UDP source port or an even UDP destination port?

The source port is irrelevant. Its the destination port.

-Jonathan R.

-- 
Jonathan D. Rosenberg                       200 Executive Drive
Chief Scientist                             Suite 210 
Dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

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From: Stephen Casner <[email-masked]>
Date: Thu, 28 Oct 1999 23:55:02 -0700 (Pacific Daylight Time)

> Does RTP use an even UDP source port or an even UDP destination port? 

This paragraph refers to the destination port number.  I will clarify
this in the text.
							-- Steve

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From: Dean Willis <[email-masked]>
Date: Thu, 28 Oct 1999 13:31:02 -0500

RTP traditonally uses an even destination port number. I believe the source
port number to be indeterminate, and have seen even, odd, and downright
random implementations.

One of the big problems we're seeing in SIP-PSTN gateway work is port number
and the description thereof in SDP. As used, the SDP only specifies the
destination port number (and IP address) and says nothing about the source.
It is quite legal to use a model where, for one "end" of the conversation,
one host is listening and an entirely different host is sending. The other
end has no information about where the stream is coming from. This makes
writing a dyamically stateful firewall very difficult. It also caused a
number of SIP implementations to blow chunks at the last bakeoff.

--
Dean

> -----Original Message-----
> From: Parekh Rishabh-crp049 [mailto:[email-masked]]
> Sent: Wednesday, October 27, 1999 9:16 AM
> To: [email-masked]'
> Cc: Mike Korus (E-mail)
> Subject: RTP port range question
>
>